Hearable eNoise Reduction - Battery Ripple Containment

ABSTRACT

The subject matter described herein provides systems and techniques for controlling the production of eNoise in an audio playback system. The eNoise may be an audible noise produced when a current, such as a noise/ripple current, flows through a battery of the audio playback system. Such eNoise may be reduced by limiting the current, such as noise/ripple current, flowing through the battery. In some examples, the noise/ripple current may be diverted to the main board of the audio playback system by adding a source of current. A circuit to produce such a current may include transistor(s), capacitor(s), and/or resistor(s). Using the current source and/or such a circuit may also divert the noise/ripple current away from the battery, thereby reducing the eNoise produced.

BACKGROUND

Electronic noise, also known as eNoise, may occur in audio playbacksystems. The eNoise may manifest itself in the form of a static and/orbuzzing sound that may be heard by the user of the audio playback systemas distortion during audio playback. In some examples, eNoise may causeusers of the audio playback system a great deal of dissatisfaction withthe quality of the audio playback system and its ability to play backaudio. It may also cause these users irritation, discomfort, anddisutility. In some examples, the presence of a battery in the audioplayback system, along with a noise/ripple current flowing through thebattery, may be a cause of the eNoise. The eNoise may be in the form ofnoise in or around the 800 Hz frequency and its harmonics. For example,a magnetic field generated by current flowing through the battery mayinteract with the magnet(s) of the audio playback system to produce theeNoise.

BRIEF SUMMARY

The present disclosure is directed to controlling the production ofeNoise in an audio playback system. As described above, the eNoise maybe an audible noise produced when a current, such as a noise/ripplecurrent, flows through the battery used in the audio playback system.Such eNoise may be reduced by limiting the current, such as noise/ripplecurrent, flowing through the battery of the audio playback system. Insome examples, the noise/ripple current may be diverted to the mainboard of the audio playback system by adding a pseudo current sourceand/or a source of current, such a circuit. Such a circuit may includetransistor(s), capacitor(s), and/or resistor(s). Using the pseudocurrent source and/or a source of current may also divert thenoise/ripple current away from the battery used in the audio playbacksystem. This may allow for any eNoise produced in the audio playbacksystem to be reduced.

In general, one aspect of the subject matter described in thisspecification includes circuitry in an audio playback system. Thecircuitry may include a decoupling capacitor, a battery, and a currentsource. The decoupling capacitor may be associated with a systemdecoupling impedance. The battery may be electrically coupled inparallel with the decoupling capacitor. The battery may provide power tothe audio playback system. The current source may be electricallycoupled between the battery and the decoupling capacitor. The currentsource may reduce eNoise in the circuitry by producing a currentdirected away from the battery. The current source may reduce a ripplecurrent flowing into the battery. The current source may be a circuitthat includes a transistor, a capacitor, and at least one resistor. Thetransistor may be a bipolar junction transistor (BJT). The transistormay be a metal-oxide-semiconductor field-effect (MOSFET) transistor. Thecurrent that may be directed away from the battery is generated at aterminal of the transistor. The eNoise may be produced by a ripplecurrent flowing through the battery. The current source may divert theripple current towards the main board of the audio playback system.Battery monitoring circuitry may be coupled in series between thebattery and the current source. The battery, the battery monitoringcircuitry, and the current source may all be electrically coupled inparallel with the decoupling capacitor. The audio playback system may bean earbud.

Another aspect of the subject matter described in this specificationincludes a system for reducing eNoise in an audio playback system. Thesystem may include a decoupling capacitor, a noise source, a battery,and a circuit. The decoupling capacitor may be associated with a systemdecoupling impedance. The noise source may be electrically coupled inparallel to the decoupling capacitor. The noise source may representeNoise in the circuitry. The eNoise may be produced by a ripple currentflowing through the battery. The battery may be electrically coupled inparallel with the decoupling capacitor and the noise source. The batterymay provide power to the audio playback system. The circuit may beelectrically coupled between the battery and the noise source. Thecircuit may reduce the eNoise in the circuitry by producing a currentdirected away from the battery. The circuit may include a transistor, acapacitor, and at least one resistor. The capacitor may be coupledbetween a base and an emitter of the transistor. The capacitor and aresistor of the at least one resistor may be coupled between a gate anda source of the transistor. The current directed away from the batterymay be generated at the collector of the transistor. The currentdirected away from the battery may be generated at the drain of thetransistor. The circuit may be associated with an impedance higher thanthe impedance of the battery and components between the battery and thecircuit.

Yet another aspect of the subject matter includes a process for reducingeNoise in an audio playback system. Power may be provided to an audioplayback system using a battery. A current directed away from thebattery may be produced using a circuit that is coupled in series to thebattery and in parallel with a decoupling capacitor. A ripple currentthat produces the eNoise may be diverted away from the battery andtowards the main board of the audio playback system using the producedcurrent. The current may be produced using a transistor, a capacitor,and at least one resistor within the circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a side view of an audio playback system, such as anearbud.

FIG. 2 depicts a cross-sectional view of an audio playback system, suchas an earbud.

FIG. 3 depicts circuitry including a battery and a noise source withinan initial audio playback system.

FIG. 4 depicts noise-reducing circuitry that includes a battery withinan audio playback system.

FIG. 5 depicts a first noise-reducing circuit that includes a transistorcircuit and a battery within an audio playback system.

FIG. 6 depicts a second noise-reducing circuit that includes atransistor circuit and a battery within an audio playback system.

FIG. 7 depicts a schematic illustration of an audio playback system inaccordance with aspects of the disclosure.

FIG. 8 is a flow diagram of an example process for reducing eNoise in anaudio playback system.

DETAILED DESCRIPTION

FIG. 1 depicts a side view of an audio playback system 100, such as anearbud. Audio playback system 100 includes magnet(s) 110. Magnet(s) 110may be used for generating audio signals and/or audio playback,assisting with generating an appropriate magnetic field for generatingaudio signals, and/or for securing the audio playback system 100 to adifferent device, such as a case that is used to hold and/or house audioplayback system 100, or the like. Magnet(s) 120 may be within a case orother device that may be used to hold and/or house audio playback system100. In some examples, magnet(s) 120 may interact with magnet(s) 110 tosecure audio playback system 100 to the case. In some examples,magnet(s) 120 may interact with magnet(s) 110 for other purposes, suchas initiating a particular event within audio playback system 100.

FIG. 2 depicts a cross-sectional view of an audio playback system 200,such as an earbud. Audio playback system 200 includes speaker 210,magnet(s) 220, battery internal P bus 230, battery 240, and batteryinternal N bus 250. The speaker 210 may be in electrical communicationwith component(s) within the audio playback system 200. Thesecomponent(s) that are in electrical communication with the speaker 210may provide signals to the speaker 210 to emit audio signals, such assounds, noise signals, anti-noise signals, or the like. These emittedaudio signals may be output by the audio playback system 200 and mayenter a user's ear. Magnet(s) 220 may be used for generating audiosignals and/or audio playback, assisting with generating an appropriatemagnetic field for generating audio signals, and/or for securing theaudio playback system 200 to a different device, or the like. Thebattery internal P bus 230 may include wiring, a thin film, or anothercomponent that includes a positive substrate.

Battery 240 may be a source of electric power consisting of one or moreelectrochemical cells with external connections for powering electricaldevices. Battery 240 may be in electrical communication and/or used forpowering component(s) within the audio playback system 200. Battery 240may be a nickel cadmium (Ni—Cd) battery, a nickel metal hydride (Ni-MH)battery, a lithium ion (Li-ion), a smart battery, or any other type ofbattery. Battery 240 may be in close proximity to magnet(s) 220 andspeaker 210 within the audio playback system 200. In some examples, thebattery 240 may be a part of electrical circuitry within the audioplayback system 200, and may have one or more currents generated by theelectrical circuitry flowing through it. In some examples, the presenceof the battery 240 in the audio playback system 200, as well asnoise/ripple currents flowing through the battery, may be a cause ofeNoise. In some examples, eNoise may be undesired noise generated byvarious electro-magnetic interactions between components within theaudio playback system 200 and output through the speaker 210. Forexample, eNoise may be in the form of noise in or around the 800 Hzfrequency, and its harmonics, output through the speaker 210. Forexample, a magnetic field generated by noise current/ripple currentflowing through the battery 240 may interact with the magnet(s) 220 ofthe audio playback system to produce the eNoise via the speaker 210. Forexample, if the circuitry of the audio playback system was operating at1 Khz, over 96% of the noise current/ripple current may flow through thebattery 240. However, the systems and techniques, as described herein,may be used to control the eNoise by, for example, limiting the current,such as noise/ripple current, flowing through the battery 240. Thebattery internal N bus 250 may include wiring, a thin film, or anothercomponent that includes a negative bus summing bar.

FIG. 3 depicts circuitry 300 including a battery 310 and a noise source330 within an initial audio playback system. Circuitry 300 includesbattery 310, protection circuit module (PCM)/power line communication(PLC) 320, noise source 330, capacitor 340, and system power rail 350.In some examples, as shown in the circuitry 300, the battery 310 and thePCM/PLC 320 may both be electrically connected in series, and bothcomponents may be connected in parallel with each of the noise source330 and the capacitor 340. The battery 310 may be similar in form andfunction to the battery 240 described in connection with FIG. 2 . Insome examples, the PCM/PLC 320 may be any components and or circuitry ofthe circuitry 300 that are disposed between the battery, such as battery310, and the other circuitry downstream of the battery. In someexamples, the PCM/PLC 320 may include circuitry that monitors the stateof component(s) of the circuitry 300, such as the battery 310, and mayassist in protecting and/or controlling these component(s). The noisesource 330 may be used to model a source of noise within the circuitry300. For example, the noise source 330 may be used to model the eNoisedescribed in connection with FIG. 2 . The noise source 330 may model thenoise on the system power rail 350. The capacitor 340 may be adecoupling capacitor, which may provide an impedance within thecircuitry 300. The capacitor 340 may be used to model the totalcapacitance on the system power rail 350. For example, the capacitor 340may include a total capacitance of C=7.2 uF, and this may be the totalcapacitance on the system power rail 350. The system decouplingimpedance of the capacitor 340, Xc, may be computed using the formulaXc=1/(2*pi*f*C), where f is the frequency at which the circuitry 300operates, and C is the capacitance of the capacitor 340. For example, iff=1 KHz, and C=7.2 uF, the system decoupling impedance Xc=22.1 ohms. Thesystem power rail 350 may be one or more wires that provides power to anaudio playback system, such as the audio playback system 200, describedin connection with FIG. 2 . In some examples, a noise/ripple current onthe system power rail 350 may flow through the decoupling capacitor 340and the battery 310. As described above, when this ripple current flowsthrough the battery 310, it may create a magnetic field that mayinteract with other one or more magnets in an audio playback system tocause eNoise to be output. Continuing with the previous example, if thesystem decoupling impedance Xc=22.1, as described above, the battery 310and the PCM/PLC 320 connection impedance may be approximately 0.8 ohms.Therefore, in this example, the battery impedance may be less than 4% ofthe system decoupling impedance when f=1 KHz.

Increasing the capacitance of the decoupling capacitor, such asdecoupling capacitor 340, by 10× may reduce the system decouplingimpedance, Xc, to around 2.2 ohms in the present example. This changemay be made in an attempt to reduce the eNoise output by the speaker ofthe audio playback system by reducing the ripple current flowing throughthe battery 310 of the audio playback system. This change may increasethe size of the decoupling capacitor 340 significantly, however, and itmay not sufficiently reduce the eNoise. For example, this change mayreduce the eNoise by about 25%.

FIG. 4 depicts noise-reducing circuitry 400 that includes a battery 410within an audio playback system. The circuitry 400 includes battery 410,PCM/PLC 420, noise source 430, capacitor 440, system power rail 450, andcurrent source 460. In some examples, as shown in the circuitry 400, thebattery 410, the PCM/PLC 420, and the current source 460 may all beelectrically connected in series, and all of these components may beconnected in parallel with each of the noise source 430 and thecapacitor 440. The battery 410 may be similar in form and function tothe battery 240 described in connection with FIG. 2 and/or the battery310 described in connection with FIG. 3 . The PCM/PLC 420 may be similarin form and function to the PCM/PLC 320 described in connection withFIG. 3 . The noise source 430 may be similar in form and function to thenoise source 330 described in connection with FIG. 3 . The noise source430 may model the noise on the system power rail 450. The capacitor 440may be a decoupling capacitor, which may provide an impedance within thecircuitry 400. The capacitor 440 may be used to model the totalcapacitance on the system power rail 450. For example, the capacitor 440may include a total capacitance of C=10 uF, and this may be the totalcapacitance on the system power rail 450. The system decouplingimpedance of the capacitor 440, Xc, may be computed using the formulaXc=1/(2*pi*f*C), where f is the frequency at which the circuitry 400operates, and C is the capacitance of the capacitor 440. For example, iff=1 KHz, and C=10 uF, the system decoupling impedance is Xc=15.9 ohms.

The system power rail 450 may include one or more wires that providepower to an audio playback system, such as the audio playback system200, described in connection with FIG. 2 . In some examples, a ripplecurrent on the system power rail 450 may flow through the decouplingcapacitor 440 and the battery 410. As described above, when this ripplecurrent flows through the battery, it may create a magnetic field thatinteracts with the one or more other magnets in the audio playbacksystem to create vibrations, which may output as noise. This eNoise maybe represented by the noise source 430. The current source 460 mayoutput a current flowing away from the battery 410 on the system powerrail 450. For example, the current may be a 5 mA current. The currentsource 460 may be used to isolate, reduce, and/or eliminate this eNoise.In some examples, current source 460 may have a high or infiniteimpedance that may be a higher impedance than the impedance of thebattery and other components that are upstream of the current source 460in the circuitry 400. As a result, in some examples, the ripple currentthat may have normally flowed through the battery 410 to cause eNoisemay instead be diverted away from the battery 410 and towards the mainlogic board of the audio playback system and dissipated through thedecoupling capacitor 440. The current source 460 may be a pseudo-currentsource. The current source 460 may be implemented using any circuitrythat outputs a current. In some examples, the current source 460 may beimplemented by circuitry that includes transistor(s), resistor(s),and/or capacitor(s).

FIG. 5 depicts a first noise-reducing circuit 500 that includes atransistor circuit 560 and a battery 510 within an audio playbacksystem. The circuitry 500 includes battery 510, PCM/PLC 520, noisesource 530, capacitor 540, system power rail 550, and circuit 560. Thecircuit 560 may include a transistor 562, such as a PNP type bipolarjunction transistor, a capacitor 564, and a resistor 566. In someexamples, as shown in the circuitry 500, the battery 510, the PCM/PLC520, and the circuit 560 may all be electrically connected in series,and all of these components may be connected in parallel with each ofthe noise source 530 and the capacitor 540. The battery 510 may besimilar in form and function to the battery 240 described in connectionwith FIG. 2 and/or the battery 310 described in connection with FIG. 3 .The PCM/PLC 520 may be similar in form and function to the PCM/PLC 320described in connection with FIG. 3 . The noise source 530 may besimilar in form and function to the noise source 330 described inconnection with FIG. 3 . The noise source 530 may model the noise on thesystem power rail 550. The capacitor 540 may be a decoupling capacitor,which may provide an impedance within the circuitry 500. The capacitor540 may be used to model the total decoupling capacitance on the systempower rail 550. For example, the capacitor 540 may include a totaldecoupling capacitance of C1=10 uF, and this may be the total decouplingcapacitance on the system power rail 550. The system decouplingimpedance of the capacitor 540, Xc, may be computed using the formulaXc1=1/(2*pi*f*C), where f is the frequency at which the circuitry 500operates, and C1 is the capacitance of the capacitor 540. For example,if f=1 KHz, and C1=10 uF, the system decoupling impedance Xc1=15.9 ohms.The system power rail 550 may be one or more wires that provides powerto an audio playback system, such as the audio playback system 200,described in connection with FIG. 2 . In some examples, a ripple currenton the system power rail 550 may flow through the decoupling capacitor540 and the battery 510. As described above, when this ripple currentflows through the battery, it may create a magnetic field that interactswith one or more other magnets in an audio playback system to causeeNoise to be output by the speaker of the audio playback system. ThiseNoise may be represented by the noise source 530.

The circuit 560 may include a transistor 562, such as a PNP type bipolarjunction transistor, a capacitor 564, and a resistor 566. In someexamples, as shown in circuit 560, a first terminal of the capacitor 564may be connected to the emitter of the transistor 562 and a secondterminal of the capacitor 564 may be connected to the base of thetransistor 562 as well as a terminal of the resistor 566. The collectorof the transistor 562 may be connected to a terminal of the noise source530. In some examples, the capacitor 564 may have a capacitance of C2,and the resistor 566 may have a resistance of R1. For example, C2=10 uF.The circuit 560 may output a current Ic from, for example, the collectorof the transistor 562. In the circuit 560, the base current, Q1 Ib, ofthe transistor 562 may be controlled by using the beta of transistor 562multiplied by the difference of battery voltage, Vbatt, and thetransistor 562 base emitter voltage, Vbe, divided by the resistance, R1,of the resistor 566. Here, the beta of transistor 562 may be anamplification factor between the base current and the collector currentof the transistor. In particular, Ib=beta*[(Vbatt−Vbe)/R1]. Thecapacitor 564 may clamp the base emitter voltage, Vbe, of the transistor562. This may allow the current, Ic, output from the collector of thetransistor 562, to act as a current source, such as the current source460 described in connection with FIG. 4 .

The current output from the collector of transistor 562, Ic, may flowaway from the battery 510 on the system power rail 550. The circuit 560and/or the current Ic may be used to isolate, reduce, and/or eliminatethe eNoise, described above. In some examples, the circuit 560 may havea high impedance that may be a higher impedance than the impedance ofthe battery and other components that are upstream of the circuit 560 inthe circuitry 500. As a result, in some examples, the ripple currentthat may have normally flowed through the battery 510 to cause eNoise,may instead be diverted away from the battery 510 and towards the mainlogic board of the audio playback system because of the circuit 560and/or the current Ic.

FIG. 6 depicts a second noise-reducing circuit 600 that includes atransistor circuit 660 and a battery 610 within an audio playbacksystem. The circuit 600 includes battery 610, PCM/PLC 620, noise source630, capacitor 640, system power rail 650, and circuit 660. The circuit660 may include a transistor 662, such as a P-channelmetal-oxide-semiconductor field-effect (MOSFET) transistor, a capacitor664, and resistors 666 and 668. In some examples, as shown in circuit660, a first terminal of the capacitor 664 may be connected to thesource of the transistor 662 as well as a first terminal of resistor668, and a second terminal of the capacitor 664 may be connected to thegate of the transistor 662 as well as a second terminal of the resistor668 along with a terminal of resistor 666. The drain of the transistor662 may be connected to a terminal of the noise source 630.

In some examples, as shown in the circuitry 600, the battery 610, thePCM/PLC 620, and the circuit 660 may all be electrically connected inseries, and all of these components may be connected in parallel witheach of the noise source 630 and the capacitor 640. The battery 610 maybe similar in form and function to the battery 240 described inconnection with FIG. 2 and/or the battery 310 described in connectionwith FIG. 3 . The PCM/PLC 620 may be similar in form and function to thePCM/PLC 320 described in connection with FIG. 3 . The noise source 630may be similar in form and function to the noise source 330 described inconnection with FIG. 3 . The noise source 630 may model the noise on thesystem power rail 650. The capacitor 640 may be a decoupling capacitor,which may provide an impedance within the circuitry 600. The capacitor640 may be used to model the total decoupling capacitance on the systempower rail 650. For example, the capacitor 640 may include a totaldecoupling capacitance of C1=10 uF, and this may be the total decouplingcapacitance on the system power rail 650. The system decouplingimpedance of the capacitor 640, Xc, may be computed using the formulaXc1=1/(2*pi*f*C), where f is the frequency at which the circuitry 600operates, and C1 is the capacitance of the capacitor 640. For example,if f=1 KHz, and C1=10 uF, the system decoupling impedance Xc1=15.9 ohms.The system power rail 650 may be one or more wires that provides powerto an audio playback system, such as the audio playback system 200,described in connection with FIG. 2 . In some examples, a ripple currenton the system power rail 650 may flow through the decoupling capacitor640 and the battery 610. As described above, when this ripple currentflows through the battery, it may create a magnetic field that interactswith the one or more other magnets in an audio playback system to causeeNoise to be output by the speaker of the audio playback system. ThiseNoise may be represented by the noise source 630.

The circuit 660 may include a transistor 662, such as a P-channel MOSFETtransistor, a capacitor 664, and resistors 666 and 668. In someexamples, the transistor 662 may have a floating gate. In some examples,the capacitor 664 may have a capacitance of C2, the resistor 666 mayhave a resistance of R1, and the resistor 568 may have a resistance ofR2. For example, C2=10 uF and/or R2 may be a large value. The circuit660 may output a current, Id, from for example, the drain of thetransistor 662. In the circuit 660, the open circuit output voltage ofthe gate of the transistor, Q1 Vg, may be controlled by using theproduct of base voltage, Vb, of the transistor, and the secondresistance, R2, of the resistor 668 divided by the sum of bothresistances, R1+R2, where R1 is the first resistance of the resistor666. In particular, Vg=Vb*R2/(R1+R2). In some examples, the particulardesign of circuit 660, including a MOSFET transistor with a floatinggate, may reduce or eliminate leakage currents. Such leakage currentsmay otherwise drain battery 610, and may occur in circuits similar tocircuit 660 designed with other types of transistors. In addition, insome examples, the particular design of circuit 660 may allow for theuse of a capacitor 664 with a relatively small capacitance. This mayallow for the reduction of the space and/or surface area used by such acapacitor and thereby may allow for the reduction in the size of thecircuit 660 and the circuitry 600.

The capacitor 664 may clamp the open circuit output voltage, Vg, of thetransistor 662. This may allow the current, Id, output from the drain ofthe transistor 662, to act as a current source, such as the currentsource 460 described in connection with FIG. 4 . The current output fromthe drain of transistor 662, Id, may flow away from the battery 610 onthe system power rail 650. The circuit 660 and/or the current Id may beused to isolate, reduce, and/or eliminate the eNoise, described above.In some examples, the circuit 660 may have a high impedance that may bea higher impedance than the impedance of the battery and othercomponents that are upstream of the circuit 660 in the circuitry 600. Asa result, in some examples, the ripple current that may have normallyflowed through the battery 610 to cause eNoise, may instead be divertedaway from the battery 610 and towards the main logic board of the audioplayback system because of the circuit 660 and/or the current Id.

Using the systems and techniques to divert the ripple current away fromthe battery used in an audio playback system, as presented herein, maysignificantly reduce eNoise. For example, using such systems andtechniques in real-world systems, eNoise may be reduced by approximately17 dB or more or less.

FIG. 7 depicts a schematic illustration of audio playback system 700.The audio playback system may be similar to audio playback system 100described in connection with FIG. 1 , and/or audio playback system 200described in connection with FIG. 2 , and/or other audio playbacksystems described herein. The audio playback system 700 may include ahousing 760 that contains various components of the system, includingduct 710, feedforward microphone 720, processor(s) 730, speaker 740, andfeedback microphone 750. Source 701 may include audio informationexternal to housing 760, including ambient noise or the like. Audioplayback system 700 may be a speaker, a headphone, an earbud, or thelike. Although not shown, audio playback system 700 may communicate witha computing device, such as a mobile phone, a tablet, a smart watch, orthe like. The computing device may provide audio playback system 700with instructions to output sounds, such as voices, music, podcasts,system alert sounds, other audio signals, or the like.

The audio playback system 700 may include other components that are notshown in FIG. 7 , such as a communication interface, wirelesstransceiver, or the like. In some examples, audio playback system 700may include a system memory, a bus, networking interface(s), and othercomponents (not shown), such as storage(s), output device interface(s),input device interface(s). A bus may be used for communicating betweenthe processor(s) 730, the system memory, the networking interface(s),and other components. Any or all components of audio playback system 700may be used in conjunction with the subject of the present disclosure.In some examples, the audio playback system 700 may include circuitry300, 400, 500, and/or 600, described above. In some examples, thecomponents within the audio playback system may be powered by thebattery in circuitry 300, 400, 500, and/or 600, described above.

Processor(s) 730 may be of any type including but not limited to atensor processing unit (TPU), a microprocessor, a microcontroller, adigital signal processor (DSP), or any combination thereof. Theprocessor(s) 730 may include one more level of caching, such as a levelone cache and a level two cache, a processor core, and registers. Theprocessor core may include one or more arithmetic logic unit (ALU), oneor more floating point unit (FPU), one or more DSP core, or anycombination thereof. A memory controller may also be used with theprocessor(s) 730, or in some implementations the memory controller canbe an internal part of the processor(s) 730. Depending on the desiredconfiguration, the physical system memory in the audio playback system700 may be of any type including but not limited to volatile memory,such as RAM, non-volatile memory, such as ROM, flash memory, etc.,multiple of these memories, other memory technology, or any combinationthereof. The physical memory may include an operating system, one ormore applications, and program data, which may include service data. Thephysical memory may be used by the processor(s) 730 to operate aspectsof audio playback system 700. The program data may be non-transitorycomputer-readable medium program data, and may include instructionsthat, when executed by the processors(s) 730, implement any process ortechnique described herein, such as process 800, described in connectionwith FIG. 8 , for reducing eNoise in an audio playback system. In someexamples, the one or more applications may be arranged to operate withprogram data and service data on an operating system.

Feedforward microphone 720, feedback microphone 750, and speaker 740 maybe in electrical communication with processor(s) 730. Such electricalcommunication may enable processor(s) 730 to analyze noise received byfeedforward microphone 720 and feedback microphone 750 while alsoproviding signals to speaker 740 to emit audio signals, such as to emitan anti-noise signal and sounds. Feedforward microphone 720 may behoused along a surface of housing 760 and may face away from thehousing. Feedforward microphone 720 may receive external noise directlyfrom source 701. Feedback microphone 750 may be housed within housing760 and may face an interior portion of the housing. Feedback microphone750 may receive external noise from source 701 through duct 710, audiosignals from speaker 740, and/or other residual noise within housing760.

Housing 760 may include an exit opening 761 leading from an interior ofthe housing to the exterior of the housing. As such, exit opening 761may allow for output from speaker 740 to exit audio playback system 700.For example, where audio playback system 700 is an earbud, exit opening761 may allow for output audio to enter a user's ear from speaker 740.In some examples, processor(s) 730 may include an active noisecancellation (ANC) system that may reduce or remove noise for the userof the audio playback system 700 based on the external noise receivedfrom the feedforward microphone 720 and/or the feedback microphone 750.Using these microphones, the ANC system may emit an anti-noise audiosignal from ambient noise, and may add this signal to the audio outputof the audio playback system 700 so that it may cancel or reduce noiseat the eardrum of the user. In addition, these microphones may be usedto generate a correction audio signal from residual noise at the speakerof the audio playback system. The correction audio signal may also beadded to the audio output of the audio playback system so that it maycancel or reduce noise at the eardrum of the user. The system/circuitryand techniques, as described herein, may improve the functioning of anaudio playback system, such as audio playback system 700, by alsoreducing eNoise for the user of the audio playback system 700.

FIG. 8 is a flow diagram of example process 800 for reducing eNoise inan audio playback system. While the operations of the process 800 aredescribed in a particular order, it should be understood that the ordermay be modified and operations may be performed in parallel. Moreover,it should be understood that operations may be added or omitted.

In block 810, power may be provided to an audio playback system using abattery. For example, power may be provided by the batteries describedin connection with circuitry 300, 400, 500, 600, and/or 700, describedabove.

In block 820, a current directed away from the battery may be producedusing a circuit that is coupled in series to the battery and in parallelwith a decoupling capacitor. The current may be produced using atransistor, a capacitor, and at least one resistor within the circuit.For example, the current may be produced by a current source, such ascurrent source 460 described in connection with FIG. 4 . For example,the current may be produced by a circuit, such as circuit 560 describedin connection with FIG. 5 and/or circuit 660 described in connectionwith FIG. 6 .

In block 830, a ripple current that produces the eNoise may be divertedaway from the battery and towards the main board of the audio playbacksystem using the produced current. For example, as described inconnection with FIG. 4 , the ripple current that may have normallyflowed through the battery 410, may instead be diverted away from thebattery 410 and towards the main logic board of the audio playbacksystem by the current source 460. For example, as described inconnection with FIG. 5 , the ripple current that may have normallyflowed through the battery 510, may instead be diverted away from thebattery 510 and towards the main logic board of the audio playbacksystem because of the circuit 560 and/or the current Ic. For example, asdescribed in connection with FIG. 6 , the ripple current that may havenormally flowed through the battery 610, may instead be diverted awayfrom the battery 610 and towards the main logic board of the audioplayback system because of the circuit 660 and/or the current Ic.

Aspects of the present disclosure may be implemented as a computerimplemented process, a system, or as an article of manufacture such as amemory device or non-transitory computer readable storage medium. Thecomputer readable storage medium may be readable by an electronic deviceand may comprise instructions for causing an electronic device or otherdevice to perform processes and techniques described in the presentdisclosure. The computer readable storage medium may be implemented by avolatile computer memory, non-volatile computer memory, solid statememory, flash drive, and/or other memory or other non-transitory and/ortransitory media. Aspects of the present disclosure may be performed indifferent forms of software, firmware, and/or hardware. Further, theteachings of the disclosure may be performed by an application specificintegrated circuit (ASIC), field programmable gate array (FPGA), orother component, for example.

Aspects of the present disclosure may be performed on a single device ormay be performed on multiple devices. For example, modules including oneor more components described herein may be located in different devicesand may each perform one or more aspects of the present disclosure. Asused in this disclosure, the term “a” or “one” may include one or moreitems unless specifically stated otherwise. Further, the phrase “basedon” is intended to mean “based at least in part on” unless specificallystated otherwise.

The above aspects of the present disclosure are meant to beillustrative. They were chosen to explain the principles and applicationof the disclosure and are not intended to be exhaustive or to limit thedisclosure. Many modifications and variations of the disclosed aspectsmay be apparent to those of skill in the art.

Unless otherwise stated, the foregoing alternative examples are notmutually exclusive, but may be implemented in various combinations toachieve unique advantages. As these and other variations andcombinations of the features discussed above can be utilized withoutdeparting from the subject matter defined by the claims, the foregoingdescription of the examples should be taken by way of illustrationrather than by way of limitation of the subject matter defined by theclaims. In addition, the provision of the examples described herein, aswell as clauses phrased as “such as,” “including” and the like, shouldnot be interpreted as limiting the subject matter of the claims to thespecific examples; rather, the examples are intended to illustrate onlyone of many possible examples. Further, the same reference numbers indifferent drawings can identify the same or similar elements.

Numerous examples are described in the present application, and arepresented for illustrative purposes only. The described examples arenot, and are not intended to be, limiting in any sense. One of ordinaryskill in the art will recognize that the disclosed subject matter may bepracticed with various modifications and alterations, such asstructural, logical, software, and electrical modifications. It shouldbe understood that the described features are not limited to usage inthe one or more particular examples or drawings with reference to whichthey are described, unless expressly specified otherwise.

1. Circuitry in an audio playback system, the circuitry comprising: adecoupling capacitor associated with a system decoupling impedance; abattery, electrically coupled in parallel with the decoupling capacitor,the battery providing power to the audio playback system; and a currentsource electrically coupled between the battery and the decouplingcapacitor, wherein the current source reduces eNoise in the circuitry byproducing a current directed away from the battery.
 2. The circuitry ofclaim 1, wherein the current source reduces a ripple current flowinginto the battery.
 3. The circuitry of claim 1, wherein the currentsource is a circuit comprising a transistor, a capacitor, and at leastone resistor.
 4. The circuitry of claim 3, wherein the transistor is abipolar junction transistor (BJT).
 5. The circuitry of claim 3, whereinthe transistor is a metal-oxide-semiconductor field-effect (MOSFET)transistor.
 6. The circuitry of claim 3, wherein the current directedaway from the battery is generated at a terminal of the transistor. 7.The circuitry of claim 1, wherein the eNoise is produced by a ripplecurrent flowing through the battery.
 8. The circuitry of claim 7,wherein the current source diverts the ripple current towards the mainboard of the audio playback system.
 9. The circuitry of claim 1, furthercomprising battery monitoring circuitry coupled in series between thebattery and the current source.
 10. The circuitry of claim 9, whereinthe battery, the battery monitoring circuitry, and the current sourceare all electrically coupled in parallel with the decoupling capacitor.11. The circuitry of claim 1, wherein the audio playback system is anearbud.
 12. A system for reducing eNoise in an audio playback system,the system comprising: a decoupling capacitor associated with a systemdecoupling impedance in the system; a noise source, electrically coupledin parallel to the decoupling capacitor, the noise source representingeNoise in the circuitry, wherein the eNoise is produced by a ripplecurrent flowing through the battery; a battery, electrically coupled inparallel with the decoupling capacitance and the noise source, thebattery providing power to the audio playback system; and a circuitelectrically coupled between the battery and the noise source, whereinthe circuit reduces the eNoise in the circuitry by producing a currentdirected away from the battery.
 13. The system of claim 12, wherein thecircuit includes a transistor, a capacitor, and at least one resistor.14. The system of claim 13, wherein the capacitor is coupled between abase and an emitter of the transistor.
 15. The system of claim 13,wherein the capacitor and a resistor of the at least one resistor arecoupled between a gate and a source of the transistor.
 16. The system ofclaim 14, wherein the current directed away from the battery isgenerated at the collector of the transistor.
 17. The system of claim15, wearing the current directed away from the battery is generated atthe drain of the transistor.
 18. The system of claim 12, wherein thecircuit is associated with an impedance higher than the impedance of thebattery and components between the battery and the circuit.
 19. A methodof reducing eNoise in an audio playback system, the method comprising:providing power to an audio playback system using a battery; producing acurrent directed away from the battery using a circuit that is coupledin series to the battery and in parallel with a decoupling capacitor;diverting a ripple current that produces the eNoise away from thebattery and towards the main board of the audio playback system usingthe produced current.
 20. The method of claim 19, wherein the producingthe current comprises producing the current using a transistor, acapacitor, and at least one resistor within the circuit.